Detailed subject-specific FE rib modeling for fracture prediction
Journal article, 2019

Objective: The current state of the art human body models (HBMs) underpredict the number of fractured ribs. Also, it has not been shown that the models can predict the fracture locations. Efforts have been made to create subject specific rib models for fracture prediction, with mixed results. The aim of this study is to evaluate if subject-specific finite element (FE) rib models, based on state-of-the-art clinical CT data combined with subject-specific material data, can predict rib stiffness and fracture location in anterior-posterior rib bending.

Method: High resolution clinical CT data was used to generate detailed subject-specific geometry for twelve FE models of the sixth rib. The cortical bone periosteal and endosteal surfaces were estimated based on a previously calibrated cortical bone mapping algorithm. The cortical and the trabecular bone were modeled using a hexa-block algorithm. The isotropic material model for the cortical bone in each rib model was assigned subject-specific material data based on tension coupon tests.  Two different modeling strategies were used for the trabecular bone. The capability of the FE model to predict fracture location was carried out by modeling physical dynamic anterior-posterior rib bending tests. The rib model predictions were directly compared to the results from the tests. The predicted force-displacement time history, strain measurements at four locations, and rotation of the rib ends were compared to the results from the physical tests by means of CORA analysis. Rib fracture location in the FE model was estimated as the position for the element with the highest first principle strain at the time corresponding to rib fracture in the physical test.

Results: Seven out of the twelve rib models predicted the fracture locations (at least for one of the trabecular modeling strategies) and had a force-displacement CORA score above 0.65. The other five rib models, had either a poor force-displacement CORA response or a poor fracture location prediction. It was observed that the stress-strain response for the coupon test for these five ribs showed significantly lower Young’s modulus, yield stress, and elongation at fracture compared to the other seven ribs.

Conclusion: This study indicates that rib fracture location can be predicted for subject specific rib models based on high resolution CT, when loaded in anterior-posterior bending, as long as the rib’s cortical cortex is of sufficient thickness and has limited porosity. This study provides guide-lines for further enhancements of rib modeling for fracture location prediction with HBMs.

fracture

finite element

HBM

rib

subject specific

Author

Johan Iraeus

Injury Prevention

Linus Lundin

ÅF Industry

Simon Storm

ÅF Industry

Amanda Agnew

Ohio State University

Yun-Seok Kang

Ohio State University

Andrew Kemper

Virginia Tech

Devon Albert

Virginia Tech

Sven Holcombe

University of Michigan

Bengt Pipkorn

Chalmers, Mechanics and Maritime Sciences

Traffic Injury Prevention

1538-9588 (ISSN) 1538-957X (eISSN)

Vol. 20 sup2 S88-S95

Development of Implementable Omni-Directional Chest, Spine and Head Injury Criteria for Human Body Models

VINNOVA, 2016-02-01 -- 2018-12-31.

Areas of Advance

Transport

Subject Categories

Surgery

Vehicle Engineering

Public Health, Global Health, Social Medicine and Epidemiology

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

DOI

10.1080/15389588.2019.1665649

More information

Latest update

5/20/2020